The present invention relates to a face orientation detection apparatus, a face orientation detection method and a computer memory product, for detecting the orientation of a face from image data acquired by photographing the face.
As an apparatus for assisting driving of a vehicle such an automobile, there has been proposed an apparatus for detecting the orientation of a driver's face based on image data obtained by photographing the face of the driver with a camera mounted in the vehicle at a position capable of photographing the face of the driver. With the use of such an apparatus, it is possible to detect inattentive driving from the orientation of the driver's face detected by the apparatus, and also possible to build a system for warning the driver of inattentive driving (see, for example, Japanese Patent Application Laid-Open No. 6-243367/1994).
However, it is often the case that an apparatus as mentioned above is constructed to determine the orientation of a driver's face by storing image data acquired by photographing the face of the driver in a plurality of orientations in advance, comparing these image data with image data sequentially acquired when the vehicle is running, and selecting image data of an orientation having a higher degree of correlation. In such a structure, since a plurality of pieces of image data acquired by photographing the face facing respective orientations need to be stored in advance, the memory capacity for storing the respective image data is very large. Moreover, since the image data with a high degree of correlation is selected for each piece of sequentially acquired image data, it takes a long time to determine the face orientation.
Furthermore, owing to the process for judging the face orientation based on the image data acquired by photographing a predetermined driver in advance, if another driver drives the vehicle, it is impossible to judge the face orientation. Besides, even when the same driver drives the vehicle, if the distance between the camera mounted in the vehicle and the driver as an object to be photographed differs from the distance when the image data was photographed, there is a difference in the size of the face region of the driver between these image data, and it is necessary to perform an enlargement or reducing process on the face region of sequentially acquired image data. Thus, such an apparatus suffers from the problem that it can not flexibly meet various conditions. Besides, since the apparatus of Japanese Patent Application Laid-Open No. 6-243367 (1994) is constructed to extract the tear ducts of both eyes and both ends of the lips from image data acquired by photographing the face of a driver and detect the orientation of the driver's face, based on the positional relationship among the extracted four points, if sequentially acquired image data does not include the lips of the driver, for example, there arises a problem that the apparatus can not detect the orientation of the driver's face.